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Key Questions:

What is torque? How do we calculate torque?. Key Questions:. Performance Objectives. Measure forces and distances in a simple machine. Calculate torque. Apply the concept of mechanical advantage to levers. Build three classes of levers. Lever Assembly. SAFETY NOTE:

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Key Questions:

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  1. What is torque? How do we calculate torque? Key Questions:

  2. Performance Objectives • Measure forces and distances in a simple machine. • Calculate torque. • Apply the concept of mechanical advantage to levers. • Build three classes of levers.

  3. Lever Assembly • SAFETY NOTE: • WATCH for FALLING weights on bare toes or sandals or table tops! • DO not place the fulcrum higher than hole 3 of stand!

  4. Torque • Levers use torque to lift or move objects. • Torque is a force applied over a distance that causes ROTATION to occur. • Torque is measured in Newtonmeters (Nm)

  5. Force x Distance = Force x Distance Review of levers Input Force x Length of Input Arm Output Force x Length of Output Arm = = Torque Force X Distance

  6. An Example of Torque • Calculate the torque created when opening the door.

  7. 1. Set up the balanced lever

  8. 2. Measure Forces and 3. Calculate input/output torques

  9. Calibrate the spring scale

  10. Data

  11. Torque and direction • If more than one torque acts on an object, the torques are combined to determine the net torque. • If the torques tend to make an object spin in the same direction (clockwise or counterclockwise), they are added together. • If the torques tend to make the object spin in opposite directions, the torques are subtracted. • Torques causing counterclockwise rotation are positive and torques causing clockwise rotation are negative.

  12. The variables in a simple machine can be adjusted make work easier or resist forces on purpose. Consider two levers: Forces and Machines

  13. The advantage the simple machine gives to the user can be calculated. A machine approaches a mechanical advantage of 1, when output forces roughly equal input forces. Forces and Machines

  14. Mechanical Advantage Output force (N) MA = Fo Fi mechanical advantage Input force (N)

  15. Mechanical advantage • What is the mechanical advantage of this new lever?

  16. Torque and mechanical advantage • What’s the mathematical relationship between torque and mechanical advantage? • MA = Output Torque ÷ Input Torque

  17. Build different levers…

  18. Three Classes of Levers • First Class - fulcrum between Input and output • Second Class – output between fulcrum and input • Third Class – input between fulcrum and output

  19. Levers and the human body • Your body contains muscles attached to bones in ways that act as levers. • Here the biceps muscle attached in front of the elbow opposes the muscles in the forearm. Can you think of other muscle levers in your body?

  20. Mobiles are levers! • GREAT STEM project!

  21. Outcomes • Usescience • Thinkscientifically • Communicatetechnical ideas • Teachall students • Be science conscious NOT science phobic

  22. What questions do you have about Torque or Mechanical Advantage?

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